Method of manufacturing a transformer core construction



' June 30, 1959 A. E. FEINBERG ETAL 2,892,249

METHOD oF MANUFACTURING A TRANSFORMER com: CONSTRUCTION Filed Jan. 1o.195e 2 sheets-sheet 1 l' l 33- 'III' 36 l N w June 30, 1959 A. E.FEINBERG ETAL METHOD OF MANUFACTURING A TRANSFORMER CORE CONSTRUCTION 2Sheets-Sheet 2 Filed Jan. 1o, 195s United States Patent O METHOD FMANUFACTURING A TRANS- FORMER CORE CONSTRUCTION Albert E. Feinberg andFrank S. Endo, Chicago, Ill., as-

signors to Advance Transformer Co., Chicago, lll., a corporation ofIllinois `Application January 10, 1956, Serial No. 558,236

2 Claims. (Cl. 'Z9-155.61)

This invention relates generally to electro-magnetic devices such as thetransformers of apparatus for igniting and operating gaseous dischargedevices. Particularly the invention is concerned with the structure ofthe core and laminations making up such transformers.

The shell type of transformer core is desirable from many standpoints.It is easy to assemble, compact, results in a quiet transformer, andusually provides at least one complete unbroken magnetic circuit in theframe. By reference to the designation shell type it is intended todesignate a type of core structure in which there is a usually elongaterectangular outer frame member having parallel elongate side partsbridged at their ends by short bridging portions maintaining the spacingacross the narrow dimension of the frame member. A central winding legextends along the core, being matingly engaged at its ends with therespective bridging portions. The side parts have windows punched onopposite sides of the winding leg so that coils mounted on the windingleg or bar will be positioned in the windows. Extensions may be providedto separate adjacent windows and form shunts.

The shell type core is usually formed of stacks of laminations in whichthose laminations stacked to pro vide the central winding leg have beenpunched out of the center of laminations which thereafter form theframing portion. The material punched out to form the windows is scrap,which is quite substantial in the shell type core. Obviously scrapincreases costs and ultimate prices to consumers.

The invention herein also utilizes a shell type core but not of theconstruction in which the frame portion is an integral member, that isto say an unbroken member formed of a stack of rectangular one piecelaminations. The primary object of the invention is to provide a coreconstruction of shell type made up of laminations so formed and shapedas to produce an extremely small quantity of scrap, while providing ahighly eifective, electrically and magnetically eicient transformercore.

The invention contemplates the mating formation of parts which will beassembled in stacks out of continuous electrical steel strips running athigh rates through automatic stamping machines. In other words, theparts of each laminated layer of the core are so arranged along acontinuous uniform width strip that the scrap is minimized.

It is understood that the mere mating arrangement of laminations orparts of laminations along electrical steel strips to decrease totalscrap generally has been known, but where special requirements demandthe provision of shunts in the core, scrapless mating of parts has notbeen accomplished to any practical degree. Even Where scrap of somequantity is expected, known structures have not achieved the highlyeconomical core of this invention and this accomplishment is anotherobject of this invention.

The novel core of the invention is made up of several parts, comprisingthe central winding leg or bar, and two 2,892,249 Patented June 30, 1959outer elongate members which are disposed on opposite sides of thewinding leg and clamped thereto and provide the framing portion. Theassemblage can be considered a unitary structure because of the abuttingjoints between tion is not so constructed.

The invention resides in the provision of a core structure formed of Tand L shaped parts forming the shell. The difference between this andprior structures, inter alia, lies in the fact that although the partsare arranged matingly along the strip from which the same are punched,the extensions which will form the shunts in the assembled core areintegral with the parts so that there is no need to insert separateshunts. One form of the invention, which is especially economical,utilizes parts which are formed in such a manner that the centralwinding leg will have indentations from the punching out of theextensions of the side parts, but such indentations are positioned at apart of the transformer where their effect upon the eicient operation ofthe transformer is practically unnoticed. l

Many objects and advantages will occur to those skilled in this art as adetailed description of specic and preferred embodiments of theinvention is set forth herein after, in connection with whichillustrations are provided for clarity and to aid in an understanding ofthe invention.

In the drawings, in which the same characters of reference are usedthroughout the several figures in order to designate the same or similarparts:

Fig. 1 is a diagrammatic top plan view of a transformer constructed inaccordance with the invention, and using the novel core of theinvention, the coils being shown in section in order better toillustrate the details.

Fig. 2 is a fragmentary top plan View of a strip of electrical steelshowing the lay-out of the parts of the core of Fig. 1 along the same toillustrate the small amount of scrap resulting from the core structure.

Fig. 3 is an electrical diagram of the circuit of the apparatus withwhich the transformer of Fig. 1 is intended to be used.

Fig. 4 and 5 illustrate ditferent layouts along strips of electricalsteel for a slightly modified form of the invention, but in which thereis slightly more scrap resultmg.

Fig. 6 is another illustration of a layout of parts of a core along asteel strip, the view being quite similar to that of Fig. 2, but theform of the invention being subtantially identical to that of Figs. 4and 5.

Looking tirst at Fig. 1, there is illustrated a transformer 10 which isformed of a so-called iron core 12 which shortly will be described indetail. The transformer 10 is intended to be connected into a circuitfor igniting and operating two gaseous discharge devices in a mannerillustrated in Fig. 3. There the transformer core is shown to mount fourwindings comprising a primary winding P connected across a relativelylow Voltage A.C. line 14, a tirst secondary Winding S1 which is spacedfrom the other windings along the core 12 and separated therefrommagnetically by means of a shunt 16, a second secondary winding S2, andan extension of the second secondary winding which is designated S21.The windings are connected end to end in order named, but the physicalplacement on the core 12 is otherwise. The tirst secondary winding S1 isdisposed on the left hand end of the core 12 as viewed in Fig. 1, andthe second secondary winding S2 is disposed on the right hand end. Theprimary winding P is in the center of the core and alongside the windingS2 and separates the winding S3 from its extension S2'.

As shown in the circuit diagram of Fig. 3, there is a gaseous dischargedevice such as a fluorescent lamp L1 connected in series with acondenser C and together therewith connected across the winding S1.There is a second lamp L2 which is connected across all of the windings.In operation, the lamp L1 lights iirst after which the lamp L2 lights,and, by virtue of the placement of'the` winding S1 and the shunt 16,current principally liows in series through the lamps and the windingsS3 and S2 and the condenser C. The exact manner of operation isdescribed in U.S. Letters Patent No. 2,683,243 olf` A. Feinberg, one ofthe applicants herein.

It` be seen that the construction of the core is such as to accommodatethe windings described, provide theA necessary shunt, and the air gapsand magnetic structure. is done in theinvention, without losing anyofthe advantagesaccruing by virtue of the highly construction of thecore and the formation of the'laminations thereof from strips of steelin the manner described in detail hereinafter.

The core 12 is formed of three stacks of laminations hdd, L Seh in anysuitable manner by clamps or other fastening devices which are wellknown and need not be shown. There is a T-shaped central winding leg orbar 20., the cross; head 22 of which is shown at the right hand end inFig. l forming the bridging magnetic connection of that end. Spacedinwardly of the right hand end there isprovided a slot 24, the purposeofwhich is' to improve wave shape in the manner described in Paul Bergerapplication for Letters Patent Serial No. 503,163 filed April 22, 195,5.There is also a pair of identical side legs 26. L-shaped with the short.leg 28 Aof each facing inwardly abutting the left end of the centralwinding leg or bar 20 on opposite sides thereof and making magneticconnection therewith at 30. The right hand end of the side legs 26 meetthe` outer ends ofk cross head 22 in similar abutting joints 32.

The. windings described are.y mounted along the central windingleg orbar 20 in the order also set forth, and ther shunt 16 is disposedbetween the winding S1 and Szf. The shunt 16V is formed by means of theinwardly extending lugs 34 integral with the side legs 26 and 27. Theends of the lugs are spaced from the sides of the central winding leg bysome predetermined amount in order to provide the usual air gaps 36 ofsuch shunts.

Attention is invited to the recesses 38 which are provided in thecentral winding leg 20 between the shunt i6 and the` left hand end ofthe core 12. These recesses are completely covered by the firstsecondary r winding S1 which is the high leakage reactance winding oflthe appar atus,'and which carries very little current, compared Ito theother windings of the transformer 10, once' the lamps are ignited. Ithas been found that positioning the recesses beneath the coil of thewindingrSl prevents the leakagev which might be. caused byv such aAr'ecessffrorn producing noise in the cannister containingthe apparatus.Also, since this winding will carry little current duringthe operationof the lamps, the eiiects of high f luxpdensity onwave shape caused byan effective narrow cross sectionV of` the central winding leglaresubstantially reduced.

Since the adverse effects of the recesses 38 are tolerable because ofthenature of the operation of the transformer, it is possible` toproduce the parts of the transformer coreI `12Vvery economically.

In; orderA to avoid confusion herein, the same characters of` referencewill be used to designate the stacked partsof thecore 12andtheindividual laminations used to makeup such stacks.` Thus, in Fig.2 which shows a single,thickness. of a steel strip having parts oflaminationslaidlout thereon, the reference character 20 designates alamination intended to be combined with identical laminations in a stackto form the T-shapedcentral These side legs or parts are,

winding leg 20. Likewise the individual stampings 26 will be used tomake the side legs 26.

The strip of electrical steel 40 has the parts 20 and 26 laid outthereon in groupings of two side legs and one central winding legdisposed therebetween. The central winding leg part 20 however isshifted to the right relative the side legs 26 when compared with theeventual position in the assembled core. Thus, the side leg parts ofeach group are laterally closer together and the end of the centralwinding leg is abutted against the inside of the short legs of the sidelegs at 42, with the cross head 22 outside the right hand end of theside legs 26. The extensions 34 are punched out of the body of thecentral winding leg parts 20 giving rise to the recesses 38 referred toabove.

With the layout described the amount of scrap is extremely small. Allscrap areas in the drawings are shaded and marked S to identify thesame, and it will be seen that the areas of Fig. 2 are quite small.There is one area and an area 46 for every group of parts.

The groups are arranged side by side with the backs of parts 26 abuttingalong lines 48.

When the parts are stacked and assembled, the central winding leg 20 isshifted to the left, the side legs 26 being spread to accommodate-thesame, resulting in the structure of Fig. l which provides-the necessarywindows for the windings.

In certain structures it might be disadvantageous to have the recesses38, and hence the layout of parts is somewhat different. In Fig. 6 thereis illustrated a yfragment of a strip of steel, in which the centralwinding leg part 20 is shifted to the right compared to the layout ofFig. 2 so that it abuts against the side of the extensions 34. Thus allof the strip which is contained between the side legs 26 and to the leftof the end of the Winding leg 20 is scrap, designated 52. Likewise,

since the` cross head 22 `protrudes considerably beyond the ends of theside legs 26, there will be an additional irregular scrap area 54between each groupof' parts. The side legs 26 are back to back along theline 48. The strip 50 will obviously be wider than thestrip 40 and theamount of scrap from the layout of Fig. 6 v

greater thanA from the layout of Fig. 2.

In Figs. 4 and 5 there are illustrated the layouts for parts along steelstrips 56 and 58 for forming the winding leg parts. 20 and ther sidelegparts 26 separately, instead of4 in the same operation as describedhereinabove. In' Fig. 4 the Winding leg parts 20 are formed side by sideand with heads alternately reversed to give rise to a single scrap area60 for. eachfpart. In Fig. 5 the pairs of side legs- 26xare laid out forpunching with the short 1legs28` and extensions 34 facing but the endsreversed so that there is. mating of the parts and a minimum of scrap.The pairs are back to back. Each pair produces two irregular scrap areas62 of the same size.

lt is believed that the invention should beobvious without'furtherdescription, and it isdesired to point out that variationsin details arepossible without departing from the scope asdened inthe claims. Thestructure shown in the drawings was used in constructing apparatus whichgave successful results whenused withtwo fwatt instant start fluorescentlamps. The width of the central winding leg was approximately 1% inchesand the other' The two windows'accommodate all windings, with-thewinding S1 being 1.8 inches long,.and the other. three combined being atotal of approximately, 5 inches in` length. The condenser C was 1.74microfarads.`

Although .not illustrated, in addition `to the lscrap, which is shown inthe accompanying drawings, there may be a very narrow strip which iscalled a carrying strip alongside any of lthe wider strips illustratedfor the purpose of supporting the partly punched laminations duringprogrcssive movement through the die. The use of carrying strips is atechnique Well known in the art. in addition, although not illustrated,the corners of the side parts 26 may be notched for the seating ofclamps. This also is known and need not be illustrated.

What it is desired to secure by Letters Patent of the United States is:

1. A method for producing a shell-type transformer core which iscomprised of individual laminations of electrical 4steel stacked andarranged together in a unitary core structure and in which theindividual laminations consist only of an elongate T-shaped member andan elongate L-shaped member, said T-shaped members are stacked to formthe central winding bar of the core and said L-shaped members arestacked and arranged with respect to the stack of T-shaped members toform the side parts of the core, the lengths of side parts are equal andthe sum of the width of the long leg of the T-shaped lamination plustwice the maximum length of the short leg of the L-shaped lamination isequal to the maximum length of the crosshead of the T-shaped laminationplus twice the Width of the Ilonger leg of the L-shaped lamination, andthere is a lug integral with the long leg of the L-shaped laminationextending in the same direction as the short leg thereof: said methodcomprising, stamping said T-shaped and L-shaped laminations in acontinuous process from a sheet of electrical steel moved through astamping machine, albeit in a predetermined geometric arrangement ofsaid individual laminations along the direction of movement of saidsheet which defines groups of said laminations, each group including apair of said L-shaped laminations and one of said T-shaped ilaminations,each T-shaped lamination having an L-shaped lamination on opposite sidesof the long leg of said T- shaped lamination with each side edge of thelong leg of the intermediate T-shaped lamination abutting a side edge ofthe long leg of one of said pair of L-shaped laminations, the cross-headof the T-shaped lamination abutting the long leg of each one of saidpair of L-shaped laminations whereby said stamping results in asubstantail reduction in waste, forming said lugs at the `same time ofstamping on each long leg of the larninations of said pair, thereafterstacking and assembling said L-shaped and T-shaped laminations to formsaid core.

2. A method for producing a shell-type transformer core which iscomprised of individual laminations of electrical steel stacked andarranged together in a unitary core structure and in which theindividua-l laminations consist only of an elongate T-shaped member andan elongate L-shaped member, said T-shaped members are stacked to formthe central winding bar of the core and said L-shaped members arestacked and arranged with respect to the stack of T-shaped members toform the side parts of the core, the lengths of side parts are equal andthe sum of the width of the long leg of the T-shaped lamination plustwice the maximum length of the short leg of the L-shaped lamination isequal to the maximum length of the cross-head of the T-shaped laminationplus twice the width of the longer leg of the Lshaped lamina tion, andthere is a lug integral with the long leg of the L-shaped iaminationextending in the same direction as the short leg thereof: said methodcomprising stamping said T-shaped and L-shaped laminations in acontinuous process from a sheet of electrical lsteel moving through astamping machine, albeit in a predetermined geometric arrangement ofsaid individual laminations along the direction of movement of saidsheet in which a pair of L- shaped laminations have the long legsthereof arranged back to back transverse to the direction of movement ofthe sheet and the short legs of the pair face in opposite directions andare approximately ush vwith a side edge of the sheet, said pair ofL-shaped laminations are spaced longitudinally along the sheet from asecond pair of L-shaped laminations `likewise arranged back to back withthe :shorter legs thereof approximately flush with the same side edge ofthe sheet, and there is a T-shaped lamination between said two pairs ofL-shaped laminations with its cross-head approximately flush with theopposite side edge of the ISheet and the end of the longer leg thereofremote from said cross-head spaced from said one side edge a distanceequal to the width of a said short leg, the side edges of the long legof the T-shaped lamination abutting the side edges of the long leg of anL- #shaped lamination of each of said pairs whereby during said stampingthere results substantial reduction in waste, and said lugs are formedduring stamping of the laminations on each long leg of an L-shapedlamination of said pair abutting the long leg of the T-shaped laminationwith accompanying formation of a recess in the said long leg of theT-shaped lamination, thereafter stacking and assembling said individuallaminations to form said core.

References Cited in the le of this patent UNITED STATES PATENTS 509,770Scott Nov. 28, 1893 1,314,051 Dorman Aug. 26, 1919 1,472,023 Koos Oct.23, 1923 1,962,431 Daley June 12, 1934 2,085,092 Furth June 29, 19372,330,824 Graniield Oct. 5, 1943 2,575,093 Bridges Nov. 13, 19512,582,291 Sola Ian. l5, 1952 2,708,741 Orsini May 17, 1955

